I'm a fourth-year undergrad student who is interested in QFT but who thoroughly dislikes the field of scattering processes and related areas, and is then very confused as to what field to pursue a PhD in. My question is whether QFT is only used to study scattering and whether there is a subfield of physics (or more!) that uses QFT for other purposes.
If by scattering processes you mean particle scattering, then the answer is emphatically no. For example QFT is used for studying many body physics and condensed matter physics and is the reigning framework for studying phase transitions.